HILL: GEOLOGY OF JAMAICA. 241 
nen Sternreihen bedeckt, die einen Querdurchmesser von 2-3 Millim, besitzen. 
Sie werden durch wenig tiefe Zwischenfelder getrennt, die in der Regel eben 
so breit sind als die Tháler und nur stellenweise, besonders an Punkten 
stärkerer Krümmung, sich mehr ausbreiten oder im Gegentheile verengern. 
Sie sind mit gedrängten, wenig ungleichen Rippehen besetzt.” 
The columella is practically the same as in D. conferticostata, sometimes 
appearing somewhat spongy. “Die Septallamellen sind gedrängt und dünn, 
an Dicke wenig ungleich. Zwischen zwei längere findet man jedoch fast 
regelmässig eine viel kürzere eingeschoben. Die längeren verdicken sich in 
der Nähe der Axe zu einem starken Knötchen, das sich mit den benachbarten 
verbindet. Die dadurch entstehende Knötchenreihe wird von der Axenlamelle 
durch eine ziemlich tiefe Furche geschieden. In der Lange eines Centimeters 
zählt man etwa 44 Septallamellen.” 
From this description three points of difference become apparent: 1st, the 
valleys in D. conferticostata are only about half as wide as in the species from 
San Giovanni Ilarione ; 2d, in the former there is not that alternation of 
longer and shorter septa characteristic of the latter; 3d, in the Jamaican species 
there is no series of fused knobs, corresponding to the inner termini of the 
larger septa, on either side of the columella, and separated from it by a rather 
deep furrow. After having made this comparison, it will be easily seen that 
the two species are very distinct; but the features that they have in common 
show them to be closely related. 
Diploria conferticostata, var. columnaris, var. nov. 
Plato XXXIX. Fig. 4. 
In the preceding discussion, I have purposely omitted the consideration of 
a specimen that seems to me to be a young one of D. conferticostata, with a 
different mode of growth. The form is a short ascending column, about 
38 mm. high, with the following dimensions. 28 mm. below the top: greater 
diameter, 18 mm.; lesser, 12.5 mm. At the top the specimen is compressed 
and has begun to bifurcate. Here the greater breadth is 22 mm.; the lesser 
varies from 2.5 to approximately 10 mm. The 10 mm. is the thickness of the 
thicker branch. The series are very long and much wound. The distance 
across the valleys is 1 to 1.5 mm.; across the collines about .5 mm. There are 
about 30 coste or septa to 5. mm., — 60 to the centimeter. The depression on 
the summit of the colline is usually very obscurely or not at all marked ; in 
some places it is moderately distinct. These are the points of difference. 
The specimen is evidently immature, and I am confident that it is only a 
yonng, somewhat peculiar variety of the D, conferticostata. 
Locality. Catadupa, R. T. Hill, collector. 
Type of Variety. Museum of Comparative Zoölogy, Harvard University. 
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